While science has the power to improve our lives and cure disease, it can also be used to torture, murder, and brainwash. Here are 25 scary experiments that destroyed lives, or have the potential to unleash doomsday.

Creepy animal experiments

Pig Powder
From the University of Pittsburgh's McGowan Institute of Regenerative Medicine, comes regenerative powder. Cells are scraped from the lining of a pig's bladder, the tissue is decellulised, and then dried. From this they managed to regrow a finger. There is something chilling about the idea that dried pig organs will be used to regrow human limbs.
Source: PubMed

Advertisement

Pit of Despair
Psychologist Harry Harlow induced clinical depression in monkeys by taking young macaques that had bonded with their mother, and placing them in complete isolation, in a darkened cage, for up to ten weeks. Within a few days they became psychotic, and most could not be treated.
Source: American Journal of Psychiatry

Russians re-attaching dog heads
This infamous propaganda film from 1940 shows Soviet Dr Sergei S. Bryukhonenko removing the head of dogs, and keeping them alive on a heart-lung machine. While possibly a Soviet fake, it produced a major stir in the west.
Source: Time Magazine

Spider Goat
Nexia Biotechnologies developed a transgenic goat whose milk contains proteins like that of spider silk. The milk can then be refined into superstrong biosteel polymers. We crossed spiders with goats, with no idea of how these could impact the ecosystem. Unsurprisingly, DARPA funded it.
Source: Science

Horrifying human experiments

THN1412 Drug Trial
In 2007, drug trials started for THN1412, a leukemia treatment. It had been tested previously in animals, and was found completely safe. Generally a drug is deemed safe to test on humans when it is found to be nonfatal to animals. When testing began in human subjects, the humans were given doses 500 times lower than found safe for animals. Nevertheless this drug, safe for animals, caused catastrophic organ failure in test subjects. Here the difference between animals and humans was deadly.
Source: New Scientist

A human brain - trapped in a mouse!
Researchers at the Salk Institute in La Jolla discovered how to grow human brain cells by injecting embryonic stem cells into fetal mice. This combines the twin horrors of stem cells and transgenic research to give us either supersmart squirmy mice babies, or people with rodent brains.
Sources: Salk Institute and Washington Post

Implantable Identity Code
The first RFID implant in a human was in 1998, and since then it's been an easy option for people wanting to be a little bit cyborg. Now companies, prisons, and hospitals have FDA approval to implant them into individuals, in order to track where people are going. A Mexican attorney general got 18 of his staff members chipped to control who had access to documents. The prospect of a business forcing its employees to receive an implant of any type is creepy and totalitarian.

Stanford Prisoner Experiment
Philip Zimbardo's Stanford prisoner experiment took place in the 1970s. The psychiatrist took 24 undergraduates and assigned them roles as either prisoners or guards, in a mock prison on campus. After just a few days, 1/3 of the guards exhibited sadistic tendencies, two prisoners had to be removed early due to emotional trauma, and the whole experiment only lasted six of the planned 14 days. It showed just how easily normal individuals can become abusive, in situations where it is encouraged.
Source: Stanford University

Milgram Experiments
The infamous "shock" experiments conducted by Stanley Milgram in the 1960s showed just how far people would go, when ordered to hurt somebody else by an authority figure. The well-known psychological study brought in volunteers who thought they were participating in an experiment where they would deliver shocks to another test subject. A doctor requested that they deliver greater and greater shocks, even when the "test subject" started to scream in pain and (in some cases) die. In reality, the experiment was to see how obedient people would be when a doctor told them to do something that was obviously horrific and possibly fatal. Many participants in the experiments were willing to shock the "test subjects" (actors hired by Milgram) until they believed those subjects were injured or dead. Later, many participants claimed they were traumatized for life after discovering that they were capable of such inhumane behavior.
Source: Journal of Abnormal and Social Psychology

Hofling Hospital Experiment
In a similar vein is the Hofling hospital experiment, which involved nurses being told to administer a dangerous dose of a drug to a patient. In the Milgram experiment, it could be argued the participants didn't really know the danger of what they were doing. With Charles Hofling's work, the nurses knew exactly how toxic the dose would be, yet 21 of the 22 would still have performed the injection.
Source: Hofling CK et al. (1966) "An Experimental Study of Nurse-Physician Relationships". Journal of Nervous and Mental Disease 141:171-180.

Historical atrocities

Sigmund Freud and the case of Emma Eckstein
In the late nineteenth century, Eckstein came to Freud to be treated for a nervous illness. He diagnosed her with hysteria and excessive masturbation. His friend Willhelm Fleis believed that hysteria and excessive masturbation could be treated by cauterizing the nose, so he performed an operation on Eckstein where he essentially burned her nasal passages. She suffered horrific infections, and was left permanently disfigured as Fleiss had left surgical gauze in her nasal passage. Other women suffered through similar experiments.
Source: Freud, Surgery, and the Surgeons (via Google Books)

Nazi Experiments
The medical atrocities performed by the Nazis are well-documented, and undeniably horrifying, with Josef Mengele's work on twins being especially disturbing. What's also terrifying is how useful this information was to medical science. A large amount of our knowledge about how hypothermia and cold effect humans is based on this data. Many have raised questions about the morality of using data gathered under such horrific circumstances.
Source: JLaw

Unit 731
Slightly less well known than the Nazi experiments were the ones inflicted on the native Chinese population by the Japanese in WWII. These included vivisection without anaesthesia, induced gangrene, live weapons testing, germ warfare infections, and worse. General MacArthur granted immunity to these doctors in exchange for helping America with biological warfare research.
Source: New York Times

The Tuskegee Syphilis experiment
Between 1932 and 1972, 399 impoverished African-American farmers in Tuskegee, Alabama, with syphilis were recruited into a free program to treat their disease, but were denied effective treatment (penicillin) even after it existed. This was done as an experiment by scientists who wanted to see how the disease would progress if untreated. The leaking of this event lead to major changes in American laws on informed consent in medical experiments.
Source: Journal of Health Care for the Poor and Underserved

Mind control

Optogenetics
A biotech system that allows scientists to turn neurons in your brain on and off using different colors of light. The technique, which requires brain implants, already works in rodents, who can be compelled to turn in a specific direction. Imagine what would happen if optogenetics were used to regulate human behavior.
Source: Wired

Stimocever
José Delgado, a Professor at Yale, invented the Stimocever, a radio implanted in the brain to control behavior. Most dramatically, he demonstrated its effectiveness by stopping a charging bull with the implant. Except this thing could control peoples actions. In one case, the implant caused erotic stimulation for a woman, who stopped looking after herself and lost some motor functions after using the stimulator. She even developed an ulcer on her finger from constantly adjusting the amplitude dial.
Source: Pain journal

MK-ULTRA
MK-ULTRA was a code name for a series of CIA mind-control research experiments, heavily steeped in chemical interrogations and LSD dosing. In operation Midnight Climax, they hired prostitutes to dose clients with LSD to see its effects on unwilling participants. The very concept of a Governmental agency trying to control minds, both to boost the mental abilities of its friends, and destroy those of its enemies, is suitably horrific.
Source: CIA Library

Our new robot overlords

Robo-Rats and Cyber-Beetles
Ready for remote controlled animals to keep an eye on you? Researchers have already found ways to create cybernetic rats and beetles, both controllable via remote. If the concept of beady eyed rats watching form the shadows doesn't scare the hell out of you, then flying bugs might. Of course, the army is very, very interested in both.
Source: Technology Review and Nature

Robots That Eat
The EATR robot (Energetically Autonomous Tactical Robot), is a DARPA funded robot meant to forage for itself, by devouring biomass. While the developers swear it's strictly vegeterian, that's hardly comforting in the face of inevitable robot intelligence, and it possibly eating all our forests.
Source: Gizmodo

You don't have to be tinfoil underwear type to get uneasy about some of the bizarre projects…
Read more Read more

The Multiple Kill Vehicle (MKV)
This robot is a cluster of warheads on a single vehicle, each of which uses jets to hover, track, and then destroy incoming missiles. Just watch the YouTube video of the test of its hovering abilities, and imagine that thing coming after you.
Source: Missile Defense Agency

Self-Replicating Replicators
The RepRap project seems relatively innocent - it's just a cheap and easy program that allows hobbyists to build 3D printers. But it's main goal is to become a self-replicating device: A replicator that replicates itself. A self-replicating system, which can create mechanical objects? This could get ugly.
Source: Rep Rap Homepage

Evolving Robots
Take a bunch of cute, round robots, give them a generation lifespan two minutes, and after a few hundred generations, they evolve to cooperate, find food, and avoid pitfalls. These robots can evolve communication and intelligence, to some degree. Incredibly short lived, with the ability to evolve greater intellect. Just wait till they break out of the lab.
Sources: Technology Review and Science Direct

It could destroy the fabric of space-time . . . or not!

The Demon Core
During experiments with a sphere of plutonium nicknamed the "demon core" at Los Alamos laboratory, scientist Louis Slotin died when a screwdriver slipped and the sphere went supercritical. After the room grew hot and was suffused in a 'blue glow,' he saved the lives of seven other people, but died from severe radiation exposure.
Sources: Trinity Atomic Website and Wikipedia

The Death Ray
In his last years, mad scientist Nikola Tesla was working on a death ray (sometimes called a "peace ray"). It was a particle beam weapon that supposedly could bring down a fleet of 10,000 airplanes at 200 miles. He tried to sell the weapon, which he claimed ran via "teleforce," to the USA and a number of European countries, but none of them would take it. When your death ray is too terrifying for the US military to take, you know that's worrying.
Source: New York Times and Nikola Tesla's scientific proposal about the weapon.

Time Machine
Physicist Ronald Mallett's work is based on using a ring laser to create closed timelike curves, which may allow time travel. Possibly you would only be able to travel back in time to the point when the device was turned on. What could go wrong?
Source: Mallett's proposal for the time machine [PDF]

Large Hadron Collider
The Large Hadron Collider (LHC), located in an underground facility in Switzerland, is the world's largest particle accelerator, designed to ram protons or lead nuclei into each other at ludicrous speeds. The LHC has suffered a series of delays, and is meant to be back online in November 2009. Physicists admit there is an infinitesimal chance that it will generate a black hole that could destroy the Earth - or possibly another kind of anomaly that would eat the universe. Two scientists have even put forth the theory that the LHC is sabotaging itself from the future, to prevent us unearthing the elusive Higgs Boson particle; others have sued in the hope that they can shut down the LHC before it destroys the world.
Source: Large Hadron Collider at CERN